1. Field of the Invention
The present invention relates to a cooling device for a vehicle which cools a coolant by using a heat exchanger for cooling such as an engine radiator, a condenser, or the like which is provided in a vehicle.
2. Description of the Related Art
A heat exchanger for cooling (hereinafter called heat exchanger), such as an engine radiator which is for cooling engine cooling water, or a condenser which is a heat exchanger for cooling of an air conditioning device for a vehicle (hereinafter called air conditioner), or the like, is provided in a vehicle, for example, within the engine room. Air at the vehicle front side is introduced in as cooling wind, and, due to the introduced cooling wind passing through the engine radiator or the condenser, the cooling water or the coolant for air conditioning is cooled.
In recent years, vehicles to which idling stop control, which stops the engine when the vehicle is stopped, is applied, and hybrid vehicles in which traveling by an electric motor in addition to the engine is possible, and the like have become popular for the purposes of increasing fuel efficiency and reducing emissions and noise.
In these vehicles, when predetermined engine stoppage conditions have been satisfied from the traveling speed, the driving-operating state, and the like, the engine driving is stopped, and when restoring conditions are satisfied, control which drives the stopped engine (hereinafter called economy running control) is carried out (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-201882).
By the way, the guiding of the cooling wind to the engine radiator is carried out by a mechanical fan. Due to the engine being stopped, the driving of the mechanical fan also is stopped, and a decrease in the cooling capacity of the engine radiator or the condenser, or the like, arises.
In order to suppress this, aforementioned JP-A No. 2003-201882 proposes, when the cooling water temperature rises, prohibiting engine stoppage, and preventing the temperature of the engine cooling water from rising. However, the effects which are obtained by economy running control deteriorate.
Further, JP-A No. 8-93473 proposes simultaneously driving a water pump, which circulates engine cooling water, and a cooling fan by using a single electric motor. By using this structure, even when the engine is stopped, the cooling fan is driven and cooling of the engine can be carried out.
Moreover, as a method of suppressing a lowering of the cooling efficiency of the engine radiator or the like in a state in which the engine is stopped while ensuring the effects obtained by economy running control, for example, JP-A No. 2002-316529 also is proposed. Here, there is proposed a method of providing an electric fan, which is driven by an electric motor, for cooling of the condenser.
Further, there is proposed, when the engine is stopped, driving an electric fan and exhausting the hot air which is within the engine room (see, for example, JP-A No. 2003-237384).
Moreover, there is proposed, when carrying out guiding of cooling wind by using only electric fans, driving two electric fans in stages in accordance with the rise in the traveling speed of the vehicle or the rise in the coolant pressure of the air conditioner (see, for example, JP-A No. 2005-30363).
In this way, using an electric fan has generally been thought of as a method for cooling plural heat exchangers, such as an engine radiator and a condenser and the like, while the engine is stopped.
Further, although not a technique relating to automatic idling stop control, there is disclosed a technique of providing a mechanical fan, which is driven by the engine, and an electric fan (see, for example, JP-A No. 9-156383).
In vehicles whose engine capacity is relatively small (e.g., up to about 1500 cc), because the cooling load of the engine radiator also is small, the desired cooling effect can be obtained at the time of automatic idling stopping even by an electric fan of an output of about 200 w to 300 w. However, in cases in which the engine capacity is large, such as a large vehicle or the like such as a truck or the like for example, the cooling load of the engine radiator also is large.
Therefore, in an automatic idling stop vehicle in which a large capacity engine is installed, if an attempt is made to ensure the cooling performance of a heat exchanger at the time when the engine is stopped by only an electric fan, the fan must be made to be large, and a fan motor fan of a large output (e.g., a motor whose about is 3 Kw or the like) is needed.
In order to provide such an electric fan, a large space is needed and the consumed electric power also becomes large (e.g., at 3 Kw, about 100 A at 46 v), and therefore, there is the problem that there is a large load on the battery as well.
Further, when a compact electric fan is used in addition to a mechanical fan, in order to simultaneously cool plural heat exchangers such as the engine radiator and the condenser and the like also at times when either of the two cooling fans is operated, there is the need to dispose them so as to be lined-up in the front-rear direction of the vehicle. This is difficult because a large space is needed in the engine room.
From this, a method has been thought of in which the driving of one cooling fan is switched between the engine and an electric motor, as shown in JP-A No. 2003-239741 for example. At this time, there is also a method of using an electric motor which is equipped with a fan coupling function shown in Hatsumei Kyokai Kokai Giho (Japanese Institute of Invention and Innovation Technology Bulletin) No. 2001-43 for example.
However, even if simply the driving of one cooling fan is possible by the engine and an electric motor respectively, appropriate switching control is needed in order to carry out efficient cooling.
Further, in a vehicle, a heat exchanger for cooling such as an engine radiator or a condenser for an air conditioner or the like is disposed at the front portion of the vehicle for example, and air is introduced in as cooling wind from openings of the front grill or the bumper grill or the like. Due to this cooling wind passing through the engine radiator or the condenser, heat exchange with the coolant is carried out.
Generally, a cooling fan (a mechanical fan such as a coupling fan or the like) which is driven by the driving force of the engine is provided in a vehicle, and, due to the engine being driven, the cooling fan sucks-in air, which is at the front in the direction of forward traveling of the vehicle (hereinafter called the front of the vehicle), into the engine room as cooling wind. In this way, an increased amount of cooling wind which passes through the engine radiator is devised, and accurate cooling of the cooling water which is the coolant is carried out.
A fan shroud is provided at the periphery of such a cooling fan, and heat within the engine room (engine compartment) is prevented from circling-in due to the cooling fan being driven and the cooling efficiency is prevented from decreasing.
Further, when a fan shroud is provided, if the hot air which is in the engine room circles-in to the vehicle front side of the engine radiator from gaps between a vehicle body structural portion and the fan shroud, the cooling efficiency by the cooling wind decreases. Here, there is proposed providing a projecting portion, which projects from the engine radiator further toward the vehicle front side, and suppressing the air within the engine room circling-in to the vehicle front side of the engine radiator (see, for example, JP-A No. 2005-96684).
In diesel engine vehicles or the like which move rearward at substantially the same frequency as moving forward, in a case in which a cooling fan is provided only for times of moving forward, the desired cooling efficiency cannot be obtained at times of moving rearward. Here, there has been proposed providing cooling fans, flappers for suction, and flappers for exhaust for each of the vehicle front side and rear side, so as to sandwich a central duct at which the radiator is provided (see, for example, JP-A No. 9-216559).
In this proposal, when the cooling fan for the rear side is operated while the vehicle is moving forward for example, due to negative pressure, the flapper for exhaust provided at the vehicle front side is closed and the flapper for suction is opened, and the flapper for exhaust provided at the vehicle rear side is opened and the flapper for suction is closed.
On the other hand, from standpoints such as improving fuel efficiency and environmental problems, it is preferable to stop the engine when traveling is stopped. At this time, a mechanical fan which is driven by the driving force of the engine also stops. Here, there is proposed providing an electric fan which operates for a given time period when the engine is stopped, and discharging-out the hot air which is within the engine room by this electric fan (see, for example, JP-A No. 2003-237384).
By the way, among vehicles, there is a so-called hybrid vehicle (HV) which is provided with an electric motor in addition to the engine as the drive sources for traveling, and the driving of the engine is stopped even while the vehicle is traveling.
Further, an air conditioner, which air-conditions the vehicle cabin interior, is provided in vehicles such as automobiles and the like. In HVs and the like, there are many cases in which the air conditioner is operated even when the engine is stopped. Therefore, cooling of the condenser is needed also when the engine is stopped.
Here, it has been thought to provide plural cooling fans such as, for example, a mechanical fan which is driven by the engine, and an electric fan or the like which can be driven even while the engine is stopped.
In this case, as shown in FIG. 16, a structure has been thought of in which, when heat exchangers for cooling 300 such as an engine radiator and a condenser or the like are cooled, plural cooling fans 302, 304 such as a mechanical fan and an electric fan or the like are disposed so as to be lined-up, for example, along a direction (the transverse direction of the vehicle) orthogonal to the front-rear direction of the vehicle, and are covered by one fan shroud 306.
However, openings 308, 310 in which the cooling fans 302, 304 are disposed are formed in the fan shroud 306. When, for example, only the cooling fan 304 is operated, the air within the engine room enters-in from the opening 308 of the cooling fan 302 (between the blades of the cooling fan 302 and the fan shroud 306). There is the problem that, regardless of the fact that the cooling fan 304 is being operated, conversely, the cooling efficiencies of the heat exchangers for cooling 300 are lowered.
Further, in order to prevent this, the cooling fan 302 and the cooling fan 304 are covered by separate fan shrouds. There is the problem that the regions which can be cooled by the respective cooling fans 302, 304 are narrowed, and the desired cooling efficiency cannot be obtained.